Steel slitting lines for slitting coiled steel into thinner strips usually include a tensioning device, or tensioner, interposed between the slitter and the recoiler, or rewinder. The tensioner is used to impart tension to the strips of steel as they are recoiled in order to ensure that the coils are tightly wrapped. Such tensioners apply a single compressive force across all the strips with a pair or more of rollers or frictional engagement surfaces that span the entire width of both sides of the parallel strips to cause the recoiler to pull the strips through the tensioner, thereby tensioning the strips of steel such as described in U.S. Pat. No. 5,007,272 to Matsunaga et al.
A common problem encountered during the slitting and rewinding operation using this type of tensioner is that the strips usually do not rewind at the same tangential speed on the recoiler. As discussed in U.S. Pat. No. 3,854,672 to Tilban, U.S. Pat. No. 3,386,679 to Foulon et al., and U.S. Pat. No. 3,061,226 to Keg, this problem occurs because the varying thickness of the original coiled steel across the sheet causes the diameters of the resultant rewound strips to increase at differing rates when rewound at the same rotational speed upon the recoiler. For example, when a thicker inner strip rewinds at the same rotational speed as a thinner outer strip, the diameter of the recoiled thicker strips will increase faster than the diameter of the thinner outer strips. When this happens, the smaller diameter outer strips will move at a slower tangential speed than the larger diameter inner strips. These outer strips moving at the slower tangential speeds create varying sagging sections, or loops, between the slitter and the tensioner that grow as the coil is fed through the line.
To overcome this problem, it is known for a looping pit to be located under where the loops sag. However, the loops that would be produced by a complete coil often exceed the depth of loop pit that is economically practical to build. Therefore, when the slower loops begin to drag on the pit floor, the line has to be stopped so that the outer strips may be cut and rewound to take up the slack. An alternative is to place spacers in the smaller diameter coils at intermittent times to increase their diameters. Either method causes delays in the slitting process that increase the cost and decrease the productivity of the process. Therefore, it would be desirable to eliminate or reduce the variation in tangential rewinding speeds across a group of slit strips in order to eliminate the need to interrupt the slitting process mid-coil.